A milliliter is a very small unit for measuring liquid volume in the metric system. One milliliter equals one-thousandth of a liter, which means you'd need 1,000 milliliters to fill a 1-liter bottle. Scientists and doctors often abbreviate it as mL.

To picture a milliliter, imagine an eyedropper: one small drop is roughly one milliliter. A teaspoon holds about 5 milliliters. A can of soda contains about 355 milliliters. When a doctor prescribes liquid medicine, the instructions might say “take 10 mL twice daily,” meaning you'd measure out 10 milliliters using the little cup or dropper that comes with the bottle.

The milliliter is part of the metric system, which scientists worldwide use because it makes calculations simple: everything works in multiples of ten. While many Americans use cups and ounces for cooking, scientists, pharmacists, and doctors rely on milliliters for precision. When exact amounts matter, like mixing chemicals in a lab or measuring medicine for a baby, milliliters give you the accuracy you need.